Drumheads were made originally from animal skin and were stretched across at least one open end or mouth of a drum shell and secured in a taut condition over the mouth of the drum shell by wrapping vines or leather lace tightly around the periphery of the drum shell, thereby compressing and clamping the animal skin against the periphery of the drum shell and maintaining the animal skin in a taut condition over the mouth of the drum shell. With use, the membrane both becomes worn, and becomes loosened from its taut condition as it is pulled away from the clamping forces of the vine or leather lace. Consequently, the animal skin often needs to be replaced and to be re-stretched in a relatively more taut condition.
By stretching an animal skin over one mouth of the drum shell at a certain tension, a certain pitch is produced upon striking the animal skin, and by placing another animal skin over the other mouth of the drum shell, a different pitch may be produced from striking that other animal skin. By striking both membranes, two pitches may be selectively employed, thereby permitting more sophisticated sounds to be produced by the drum.
In another aspect, each one of a plurality of drums may have different tensioning of the drumheads, such that an ensemble of drums can produce an elaborate variations of pitches in the sounds created by the drum ensemble.
Drumheads have been more recently fashioned of materials other than animal skin. In the mid-1900's, plastic drumheads were made from polyester that were cheaper, more durable, and less sensitive to weather than animal skins. Recently, drumheads have been fashioned of other plastic materials, such as mylar, and aramid fiber, such as kevlar.
Mechanisms for producing tension in the drumhead have also become more sophisticated. For example, a wooden or metal hoop or rim may be placed over the membrane such the membrane is squeezed between the inner periphery of the rim and the outer periphery of the drum shell. Thereafter, the rim may be moved forcefully away from the mouth of the drum shell such as with turnbuckle assemblies whereby the rim translates along the outer periphery of the drum shell and pulls the membrane along with it. Due to the compression of the membrane between the rim and the outer periphery of the drum shell, the membrane is stretched tighter across the mouth of the drum shell. The turnbuckles are usually circumferentially arranged in an equi-angular array about the outer periphery of the drum shell so that the rim may be drawn substantially evenly along the drum shell and so that the tension in the drumhead is fairly evenly, uniformly maintained across the mouth of the drum shell. In a reverse manner, the turnbuckles may be rotated so as to reduce or relieve the tension on the membrane or drumhead.
It is important that the drumhead tensioning system be able to readily change the tension of the drumhead in order to produce a selected pitch, and also that the tension be fairly uniformly maintained across the drumhead, so that the pitch is essentially constant when striking the drumhead at any particular spot or region of the drumhead. Also, such a tensioning system should permit quick and easy replacement of a drumhead.
The present invention was developed with particular reference to an ancient, pitched, hand drum known as the mridangam, which was developed predominantly in southern India. One end of the mridangam drum possesses a relatively high pitched tonal drumhead, and the other end possesses a relatively low pitched bass drumhead. Each drumhead typically possesses sixteen apertures spaced equi-angularly along the circumference thereof, and a very long leather thong or strap is laced alternatively through an aperture in each of the two drumheads and is then tightened thereby to stretch each drumhead simultaneously. By shortening the effective length of the leather strap, the drumheads are more highly tensioned, and by lengthening the leather strap, the tension in the drumheads is lessened, whereby the pitch of each drumhead may be selectively, though interdependently, tuned.
Some of the problems associated with the foregoing drumhead tensioning system for a mridangam are that both drumheads are tuned interdependently of each other, and not independently of each other, thereby tending to restrict the range of pitches that may be obtained from the drumheads. Perhaps an even greater challenge posed by this system is the gradual slackening of tension (and corresponding pitch) applied to the drumheads over time, which is exacerbated in colder climates due to the nature of the leather strapping. Finally, the traditional tuning system makes convenient and efficient replacement of drumheads by the practitioner a virtually impossible task.